This invention relates to an electronic musical instrument and, more particularly, to a digital electronic musical instrument having a multipeak filter characteristic.
The frequency spectrum of the sound produced by natural musical instruments such as violins, cellos and oboes includes a number of resonance peaks and the amplitudes of respective harmonic components are varied in an extremely complicated manner under vibrato performance so that the construction of the spectrum varies with time in an extremely complicated manner. Such complicated variation with time of the spectrum construction including many resonance peaks characterizes the tone of the natural musical instruments. Such spectrum having many resonance peaks can be realized by using a filter having multipeak characteristic (comb shaped filter). A prior art multipeak filter comprises an analogue circuit wherein a plurality of resonance circuits having different resonance frequencies are connected in parallel and an analogue tone source signal is applied to the parallel circuits. It is difficult in such multipeak analogue filter to vary its characteristic with lapse of time, once the characteristic has been set. Even if the characteristics is not required to be varied with time, but merely required to be changed to another characteristic, it is necessary to vary constants of various resonance circuit elements, for instance capacitors or inductance coils; which is extremely troublesome. For this reason, it has been extremely difficult to vary the multipeak spectrum construction with time for simulating tones of a natural musical instrument.